1. Field of the Invention
This invention concerns a method and a machine for automatic pruning of a vine grown according to the cordon leading method or so-called “Royat cordon” under which at least one fruit-bearing shoot or cordon is attached around a horizontal carrier wire, generally through spiral winding of said cordon.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
In the field of viticulture, there exists stiff competition between producers worldwide. Prices are one of the determining criteria to remain competitive. These prices result, for a large part, from growing methods implemented at the vineyards. Mechanization of the vine-growing operations, such as for example, pre-pruning, topping, harvesting, and processing of the crop made it possible to reduce the labor items and thus to reduce the production costs. However, pruning is the most costly labor item as it always requires a manual reworking phase after the mechanical pre-pruning of the vine. Vine mechanical pre-pruning indeed makes it possible to cut off and clear the maximum of stocks or shoots whose tendrils are attached to the railing wires at a close distance of the cordon. However, pre-pruning does not make it possible to control with precision the length of the stocks that must remain attached to the cordon, and therefore neither the number of fruit-bearing eyes or buds on those stocks. Therefore, manual reworking has to be done after the pre-pruning to adjust the length of the stocks to the number of eyes to be kept. In addition, the purpose of such manual reworking is to remove the disregarded stocks, in particular laterally and below the cordon, as well as the new growths on the trunk. Furthermore, the purpose of manual pruning is to ensure the precision of the pruning, which enables the grape growers to establish the desired production yield so as to maintain the quality of the quantity of wine produced. A major disadvantage of manual pruning is the time required to carry it out, which represents a major percentage of the production cost.
In order to improve the results of the pre-pruning operation, the applicant invented a method and device to analyze the structure of crop-bearing hedges (WO2004/089063) that, associated to a pre-pruning machine, for example, of the type described in European Patent No. 0312126, permits to maintain the cutters of the pre-pruning machine above and at a sufficient distance of the cordon, so as to prevent any potential damage to the latter and to avoid the removal of fruit-bearing eyes that it is desirable to keep, while keeping the pruned stocks or shoots the shortest possible.
Indeed, if it is possible to adjust the height of the machine cutters at the start of a row, their position in relation to the cordon may be modified during their movement along that row because of soil unevenness so that in case of sudden drop resulting of the machine going over a dip of the ground, the cordon can be damaged or stripped of its fruit-bearing eyes.
The pre-pruning machines equipped with a fruit-bearing hedge structure analysis device, as described in WO2004/089063 document do not allow for:                a sufficiently precise cut to forgo a later pruning operation or to significantly limit the manual reworking time; or        pruning of stocks growing laterally or below the cordon.        